Isolated articular cartilage defects and generalized cartilage disease, athroses and arthritis, respectively, in human and animal joints have certain surgical treatment options, which attempt to mimic or recreate normal anatomy and joint mechanics and/or relieve symptoms of discomfort, instability, or pain. Isolated disease often progresses to generalized disease, or arthritis—the process is a continuum. Generalized arthritis may also develop without known prior isolated disease. Arthritis may be present as a uni-, bi-, or tri-compartmental disease.
Uni-compartmental arthritis is typically less amenable to surgical options used for smaller isolated articular defects. With advanced cartilage degeneration and joint space narrowing, there is typically increased axial deformity and misalignment. Surgical options include osteotomy or uni-compartmental replacement. Options for bi- or tri-compartmental arthritis are combined procedures or total knee replacement.
Cartilage disease has been previously addressed by various means of replacing or substituting the damaged cartilage. Microfracture or abrasionplasty is a form of irritating exposed bone to create replacement fibrocartilage, but the resultant material is inferior to native cartilage. Osteochondral transplant replaces plugs of diseased cartilage and accompanying subchondral bone with grafts from either the patient or human cadaver. Small discrete lesions work well, but larger lesions, bipolar disease, and diffuse disease are not well addressed. Chondrocyte implantation harvests the patient's cartilage cells, grows them, and re-implants them on the bony bed, and covers them with a periosteal patch. Each of the aforementioned techniques work best for small contained lesions, unipolar defects (i.e., one side of joint), and primarily femoral condyle lesions. Less optimal results occur with patellofemoral joint disease, and tibial sided disease.
A further method of treating cartilage disease is to realign the joint with an osteotomy. This relieves an overloaded compartment, transferring stress to a less diseased compartment. Success of this method involves avoiding non-union and other complications, and requires prolonged non-weight bearing activity and eight to twelve months to realize clinical benefits. Only patients with mostly uni-compartmental disease are candidates. Osteotomy also complicates latter joint replacement.
Arthroscopy is used to treat other causes of pain from arthritis, namely, loose bodies, loose or frayed cartilage, meniscus tears, and synovitis. These are temporizing measures.
The end stage of cartilage disease is to perform total joint reconstruction. This type of procedure presents a prolonged recovery time and surgical risks. Because total joint prostheses are fabricated of metal and plastic, revision surgery for worn-out components is fraught with much higher complications than primary surgery, and is inevitable if the patient lives much beyond ten years.
Not much is known about the cause and progression of arthritis. With current diagnostic techniques such as MRI and bone scintigraphy, more has been elucidated about the disease process. In particular, the subchondral bone plays an important role in the initiation and progression of arthritis. Arthritis is a disease of not just the cartilage, but the underlying subchondral bone as well. Most of the clinical research to date is focused on cartilage regeneration/replacement and not on the underlying bone health.
Traditionally, cartilage has been viewed to be avascular, with diffusion of nutrients occurring from within the joint. Studies have confirmed, however, that subchondral bone is a source of vascular and nutritional support for cartilage. With age, vascular and structural support from the subchondral bone diminishes, allowing arthritic disease to progress. Namely, the inability of the bone to adequately repair itself as increasing damage occurs starts a cycle of further destruction, interfering with cartilage vascular supply and structural support.
As cartilage wear occurs, the primary functions of cartilage—to provide a low-friction bearing surface and to transmit stresses to the underlying bone—are diminished. Bone is most healthy when resisting compressive stresses. The shear stresses from the joint are partially converted to compression and tension via the architecture of the cartilage baseplate, the layer between the cartilage and underlying bone is undulating. Further, by virtue of the ultra low friction surface of cartilage on cartilage (20× lower friction than ice on ice), shear stresses are mostly converted to longitudinal. The subchondral bone is the predominant shock absorber of joint stress. Via its arch-like lattice-work of trabecular bone, stresses are transmitted to the outer cortices and ultimately dissipated. Cartilage itself does very little shock absorption secondary to its shear thickness and mechanical properties.
Bone is the ultimate shock absorber, with fracture being the endpoint of force attenuation. Trabecular microfractures have been shown to occur in locations of bone stress in impulsively loaded joints. Every joint has a physiologic envelope of function—when this envelope of function is exceeded, the rate of damage exceeds the rate of repair. As cartilage disease progresses, subchondral bone is less able to dissipate the stress it encounters, i.e., shear-type stresses. The attempts of subchondral bone to heal and remodel are seen as arthritis progresses—osteophyte formation, subchondral sclerosis, cyst formation, and subchondral MRI-enhanced changes, and increased signal on bone scintigraphy. Joint deformity from these changes further increases joint reaction force. Cartilage homeostasis is compromised—structural, vascular, neural, and nutritional.
Clinical success of current cartilage surgery is limited as it generally only works for small, uni-polar (one-sided joint) lesions of the femoral condyle. No current treatment exists for bone edema or osteonecrosis of the knee.
It would be desirable to have a minimally invasive joint support and subchondral support system and method of use of same that specifically addresses the subchondral bone in arthritic disease process and progression, and relieves the pain that results from diseased subchondral bone and the spectrum of symptoms that result from arthritis, including pain, stiffness, swelling, and discomfort. It would be further desirable to have a joint support and subchondral support system and method of use of same that provides as follows: (1) a treatment specifically for bone edema and bone bruises and osteonecrosis that has previously not existed; (2) structural scaffolding to assist in the reparative processes of diseased bone next to joints; (3) shock absorbing enhancement to subchondral bone; (4) compressive, tensile, and especially shear stress attenuation enhancement to subchondral bone; (5) a means to prevent further joint deformity from subchondral bone remodeling such as osteophyte formation; (6) assistance in the healing of or prevention of further destruction of overlying cartilage by maintaining and allowing vascularity and nutritional support from subchondral bone; (7) assistance in the healing of or prevention of further destruction of overlying cartilage by providing an adequate structural base; (8) a minimally invasive alternative to total joint reconstruction that also does not preclude or further complicate joint reconstruction; (9) a treatment for subchondral bone disease in its role in arthritis and delay or halt further progression; (10) an implant for arthritis that is minimally subject to loosening or wear, as it is integral to the trabecular framework it supports; (11) an alternative for tibial sided, patellofemoral, and bipolar disease (tibial-femoral) that is relatively easy to perform, as an adjunct to arthroscopy, and as an outpatient procedure with minimal downtime for the patient; (12) a treatment for arthritis that allows higher lever of activity than that allowed after joint resurfacing or replacement; (13) a cost effective alternative to joint replacement with less issues about the need for revision and surgical morbidity, especially in countries with less medical resources; and (14) a treatment option in veterinary medicine, specifically in equine arthroses and arthritides, among other desirable features, as described herein.